Fire vent hatch

ABSTRACT

A fire vent hatch has a housing with upstanding sidewalls and a cover pivotally secured to one of the sidewalls. A pair of rams are mounted on the housing to raise the cover, the rams being connected to a sealed container containing gas under pressure. The lower end of the rams are each pivotally connected to an arm which in turn is pivotally connected to the housing, the arms swinging downwardly when the rams are actuated. A restrictor is provided to throttle the flow of gas to the cover. A scissor latch is provided for holding the cover in the closed position. Thermally and manually controlled means are provided to release the gas to the rams and to open the latch.

United States Patent [72] Inventor Robert C. Watson Bobem ManufacturingCo. Inc., P.0. Box 32 l, Conshohocken, Pa. 19428 [21] Appl. No. 883,553[22] Filed Dec. 9, 1969 [45] Patented June29, [WI

[54] FIRE VENT HATCH 19 Claims, 6 Drawing Figs.

[52] [1.8. CI 49/7, 49/279, 49/379, 52/1 [51] 1nt.Cl l E05i15/20 [50]Field of Search 49/6, 7, 8, l, 280, 279,4,379, 139; 52/1 56 ReferencesCited UNITED STATES PATENTS 2,983,343 5/1961 Lyons 49/8 3,017,721 1/1962Wasserman 52/1 Primary Examiner-Dennis L. Taylor Attorney-Busser, Smithand Harding ABSTRACT: A fire vent hatch has a housing with upstandingsidewalls and a cover pivotally secured to one of the sidewalls. A pairof rams are mounted on the housing to raise the cover, the rams beingconnected to a sealed container containing gas under pressure. The lowerend of the rams are each pivotally connected to an arm which in turn ispivotally connected to the housing, the arms swinging downwardly whenthe rams are actuated. A restrictor is provided to throttle the flow ofgas to the cover. A scissor latch is provided. for holding the cover inthe closed position. Thermally and manually controlled means areprovided to release the gas to the rams and to open the latch.

PATENTEDJUHZQIHTI 3,589,065

SHEET 1 OF 2 IINVENTOR ROBERT c. WATSON J" BY o' 3% WV M ATTORNEYSPMENTEU June 91% SHEET 2 OF 2 m E T W A M 0 ATTORNEYS 5 NE g m o h. o 8NNNN r A g y s g N\.\ 3 mi ma NK N9 a mm N2 MN. v H m: m: 4 ll: 0 H q. 7a v2 6b EN EN 9. m. 09 9N vm om z v N: mm. H. a: w& v m m: 5 o W 1 I m Nmom .23 w ww. v .U Hi mm. w t 3 85 Wm. W h 3 N mm mm. m. 1- KNQ A}: a r9 FIRE VENT HATCH BACKGROUND OF THE INVENTION It is well known toprovide buildings with fire hatches in order to release smoke and gasesincident to a fire in order to relieve internal pressure to prevent theignition of gases and blowout of the building walls. In addition suchvents are helpful in preventing suffocation of people trapped in upperlevels of the building.

The typical fire vent is provided with springs and latches released bybreakdown of a fusible link to provide for the opening of the hatches ata predetermined temperature. Since the springs must be l ept cocked,they and their associated mechanisms such as latches and linkages areunder constant stresses. Further, in such a hatch it is difficult toprovide sufficient force to open the hatch under difficult conditions,for example, when a large amount of snow is holding down the hatch. Inaddition, such hatches are a safety hazard even prior to installationsince accidental opening in transit or during construction can be verydamaging. These problems are all solved by this invention.

SUMMARY OF THE INVENTION A fire vent hatch has a ram connected to thecover and to a source of fluid under pressure, advantageously a gas,preferably nitrogen. Preferably the. ram at its lower end is con nectedto a pivoted lever which, upon actuation of the ram, swings downwardlyto increase the angle between the ram and the cover. Also, the ramdesirably has a vent in its upper end to provide for the escape of fluidin the ram when the cover is fully opened. Means are provided to holdthe cover in the open position. The cover may be locked in the closedposition by a scissor latch. Advantageously, there is provided arestrictor to throttle the gas when it is released to the rams toprovide for a slow opening of the hatch cover. Temperature controlledmeans are provided to control the release of the fluid and the releaseof the scissor latch. This latter means has a spring which is restrainedby the use of a fusible link and a release mechanism which can beactuated manually if desired.

Typically, using a gas in a storage container under a pressure of 2,100p.s.i., a hatch of this invention has available a lifting forceinitially of in excess of 1,450 pounds as contracted to a comparablespring operated hatch which would have a lifting force in the area of150 pounds.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical section through a firevent hatch in accordance with the invention;

FIG. 2 is a view of the structure of FIG. I partially broken away andillustrating the operation of a ram;

FIG. 3 is a vertical section, partially broken away, taken on a planeindicated by the line 3-3 in FIG. 1;

FIG. 4 is a fragmentary plan view showing a portion of the quick releasemechanism;

FIG. 5 is a vertical section, partially broken away, of the gascontainer and the means for releasing the gas; and

FIG. 6 is an enlarged elevation, partially broken away, showing one ofthe latch mechanisms.

PREFERRED EMBODIMENT Referring now to FIG. I, a fire vent hatch 2 inaccordance with the invention has an upstanding rear wall 4, upstandingsidewalls 5, (only one being shown in FIG. I) and an upstanding frontwall 6. Each of the upstanding walls is bounded on its exterior side byrigid insulation 8 which lies within flashing member 10.

A cover 14 has an inner frame I6 which acts as a weather seal and whichhas a depending curb frame 18. A retaining frame is secured to frame 16by machine screws 22 and acts to hold down the entire periphery of dome24 against gasket 25 which rests on the periphery of frame 16. Frame 16has a pair of arms 26 (only one of which is shown in FIG. 1) which arefixedly secured to curb frame 18 and pivotally secured at 28 to abracket 30, each bracket 30 being secured to the portion of flashingmember 10 integral with wall 4.

As thus far described, the fire vent hatch is well known to the art andhence need not be described in any greater detail.

Adjacent each sidewall 5 there is a ram 36 having a cylinder 38 and aramrod 40 secured to a piston 42 (FIG. 2). Each cylinder 38 is pivotallyconnected to an arm 44 as indicated at 46, each arm 44 being pivotallyconnected to its adjacent sidewall 5 as indicated at 48.

A bracket 52 is secured to cylinder 38 and through which ramrod 40passes has secured thereto a washer 54 which backs up a compression coilspring 56 which in turn biases a conventional locking toggle plate 58through which ramrod 40 passes. This arrangement desirably is employedon only one of the ramrods.

The outer end of each ramrod is threadedly connected to an arm 62 whichis pivotally connected at 64 to a beam 66 which extends entirely acrossframe 16 and is fixedly secured thereto at each end thereof.

Cylinder 38 has a vent opening 70 connecting the interior of thecylinder to atmosphere permitting gases within cylinder 38 to exhaust tothe atmosphere after piston 42 clears the opening with the cover 14 inthe open position. Gas under pressure is supplied to each cylinder 38 toextend ramrod 40 through lines 72,72. Each line 72 is looped as shown at73,73 to accommodate movement of cylinders 33,38. As seen in FIG. 3,each line 72 from its associated cylinder 38 is connected to a tee 74which is threadedly connected to a restrictor 76 which is best seen inFIG. 5. Restrictor 76 has a reduced opening 78 to throttle the gaspassing therethrough and reduce the velocity at which it travels tocylinders 38,38. Restrictor 76 is threadedly connected to a fitting 78which has a bore 80 and a passage 82 providing communication betweenrestrictor 76 and bore 80. A conventional container 84 containing a gasunder pressure, preferably nitrogen, is threadedly connected at 86 tofitting 78 and abuts a sealing washer 88 which in turn abuts againstshoulder 90 of fitting 78. Container 84 has a perforatable closure seal92. A perforator 96 has a chamfered face 98 which is connected by acentral opening 100 to a side opening 102 to facilitate the flow of gasinto bore 80 after perforator 96 has pierced seal 92. Perforator 96passes through a bore 104 in fitting 78 containing packing 106.

At best seen in FIG. 3 perforator 96 is pivotally connected at I10 to aplate 112 fixedly secured to lever I14. Plate 112 is also pivotallyconnected at 116 to a lever 118 which in turn is pivotally connected at120 to lug 121 on fitting 78. A bracket 122 which is fixedly secured towall 2 supports fitting 78.

As viewed in FIG. 3 lever 114 is biased counterclockwise by an extensionspring 126 which is also connected to an eye 128 on a bracket I30secured to wall 2. The action of spring 126 is restrained by virtue oflever I14 being; connected to a fusible link 134 which in turn isconnected to looped chain 136 which is connected to looped chain 138.Each end of chain 138 has a fitting 140 with an opening 142 one of whichreceives a pin I44 passing through an opening 147 in a bracket 146secured to wall 2 and the other of which receives a fixed pin on bracket146. Pin I44 is held by the frictional engagement between the pin andthe associated fitting I42.

Depending latch member I52 and 156 are fixedly secured to frame member16 of the cover 14 and have respectively substantially horizontalportions 154 and 158 spaced below frame 16. As best seen in FIG. 6horizontal portion T54 of latch member 152 is adapted to be received inrecess 162 of a plate 164. It is also adapted to be received in recess166 of lever 168 which is pivotally secured on headed pin 170 whichpasses through lever I68 plate 164 and is secured to bracket 130. LeverI68 has an arcuate recessed portion 174 in its lower end which isadapted to receive the arcuate end 176 of lever I78 which is pivotallymounted on headed pin which passes through lever 178 and plate 164 to besecured to plate 130. The center of the arcs of portion 174 and end I76is at pin 180 which permits lever 178 to move without any movement oflever 168 but not vice versa since the distance of these arcs from pin170 is much greater than their distance from pin 180. As best seen inFIG. 3, lever 178 is connected to an extension spring 180 which engagespin 182 on lever 178 and biases lever 178 clockwise as viewed in FIG. 3.A chain 186 is also connected to pin 182 and in turn is connected tolever 114 as indicated at 188. A stop pin 192 secured to plate 164limits the movement of lever 178 counterclockwise.

Similarly the substantially horizontal portion 158 of latch 156 isadapted to be engaged by elements which are identical to the elementswhich engage latch 152 and which are given corresponding numbers. Thus,member 158 is adapted to be engaged by plate 164 and lever 168 which ispivotally mounted on headed pin 170 which passes through plate 164 andis secured to plate 202 secured to wall 2. Lever 168 has a recess forreceiving latch 156 and a lower recess 174 for receiving the upper end176 of lever 178 which is pivotally mounted on headed pin 180 whichpasses through plate 164 and is secured to plate 202. A stop 192 onplate 164 limits the movements oflever 178 clockwise. Lever 178 has apin 182 to which is secured a chain 204 which in turn is secured tolever 114 as indicated at 206.

Referring further to FIG. 3 pins 144,144 are each secured to an end ofchain loop 210 which in turn carries a pull ring 212 which can bereached from inside the building with which the hatch is employed. Loop210 is also secured to triangular plate 214 at 216. Plate 214 ispivotally mounted on wall 2 at 218 and is secured at 220 to a chain 222which passes through the adjacent sidewall 5 to the exterior of thehatch where it is connected to a pull ring 224 which is exterior of thehatch.

All parts of the above described embodiments, except the fusible link134, are of metals which readily withstand the temperature to which theymay be exposed as is conventional in such a hatch.

OPERATIONS After the hatch has been installed it is placed in theoperative condition by closing cover 14 and placing latch members 152and 154 respectively in the accommodating recesses of adjacent plates164,164. Bach lever 168 in unison with the as sociated lever 178 ismoved to a position so that recess 166 receives the adjacent latchmember and portion 176 of lever 178 meshes with recess 174 of lcver 168.Looped chain 138 is advanced to the right as shown in FIG. 3 whichcauses lever 114 and chain 186 to bring lever 178 against stop 192 andby the same token causes lever 114 and chain 204 to bring as sociatedlever 178 against stop 192. At this stage fittings 140,140 of chain 138have openings 142,142 in line with the openings in bracket 146 whichpermits pins 144,144 to be advanced through the openings in bracket 146and through openings 142,142 to secure looped chain 138.

With the plates in the positions described above, perforator 96 is inits withdrawn position. Gas container 84 can now be threadedly securedto fitting 78 to complete putting the hatch in condition for operation.At this stage it is noted that the batch is not fully armed until it isfully installed thus reducing the hazards during transit andinstallation to a minimum.

Assuming that a fire causes an elevation of the temperature sufficientto break down fusible link 134 (for example, 160 F.), the link 134 willrelease lever 114 which will be moved counterclockwise as viewed in FIG.3 by spring 126. This relaxes chain 186 which permits spring 180 to urgelever 178 clockwise as viewed in FIG. 3 leaving lever 168 free to moveclockwise. Simultaneously, the movement oflever 114 relaxes chain 204leaving the associated lever 178 free to move counterclockwise as viewedin FIG. 3. Perforator 96 penetrates seal 92 permitting the gas incontainer 84 to escape into bore 80, passage 82, through restrictor 78into pipes 72, and into cylinders 38,38 resulting in the extension ofthe piston rods 40,40 and the upward movement of cover 14. As cover 14moves upwardly latch portions 154 and 158 cam out of the associatedrecesses 162 and cam the associated levers 168 clockwise which are freeto move because of the release of levers 178,178 all as viewed in FIG.3. Lever 168 associated with latch member 156 moves the associated lever178 counterclockwise as viewed in FIG. 3. However, because of theassociated stop pin 180, lever 168 associated with latch member 154cannot move the associated lever 168 counterclockwise, but need not doso since spring 180 has already pivoted lever 178 away from theassociated lever 168.

As ramrods 40,40 extend outwardly and commence to lift hatch cover 14arms 44,44 rotate clockwise as viewed in FIG. 1 until in alignment withtheir respective rams. This increases the angle between the rams andcover 16 and provides for a larger vector of forces urging the cover 14to rotate. When the rams have rotated the cover 14 to the fully openedposition as determined by the limit of travel of pistons 42,42 withincylinders 38,38, the pistons 42,42 will have cleared the openings 70,70in their respective ram cylinders which will permit gas to exhaust fromthe cylinders and the equalization of the internal cylinder pressureswith the pressure of the atmosphere. As this occurs, the locking toggleplates 58 lock the ramrods 40 as they initiate their movement back intocylinder 38 due to the pressure drop.

After the necessity of the opening of the hatch cover 14 has passed thecover can be readily closed by first removing container 84 and thenrotating locking toggle plate 58 so as to release the frictionalengagement with the associated ramrod 40 and manually lowering the cover14. The locking of the cover 14 in the closed position is thenaccomplished as described above and a new gas container 84 can bescrewed into fitting 78 to fully return the hatch to the operativecondition.

Manual operation of the hatch in an emergency can be accomplished eitherby pulling ring 212 or ring 224 which causes the withdrawal of pin 144from the associated fitting which then permits spring 126 to rotatelever 114 to produce the same results as are produced when fusible link134 breaks down.

If it is desired to open the hatch in a nonemergency situation, gascontainer 84 can be unscrewed from fitting 78 and the pin 144 withdrawn.This causes the unlatching operation as previously described and permitsthe' raising of the cover 14 manually.

It will be understood that the above described preferred embodiment isby way of illustration and is not intended to be limiting.

Iclaim:

1. In a fire vent hatch comprising a housing having upstanding sidewallsand a cover pivotally secured to one of the sidewalls the improvementcomprising:

a ram having one end pivotally connected to the cover on an axisparallel to the pivotal axis of the cover and having the other endpivotally connected to a sidewall on an axis parallel to the pivotalaxis of the cover and lower than the pivotal axis of said one end,

removable means to store a fluid under pressure connected to the ram,and

temperature controlled means to control the flow of fluid from thestorage means to the ram to provide for the flow of fluid to the ram toraise the cover at a predetermined temperature.

2. The device in accordance with claim 1 in which said other end of theram is pivotally connected to an arm on an axis parallel to the pivotalaxis of the cover, the arm is pivotally connected to a side at a pointin a vertical plane lying intermediate the vertical plane containing thepivotal axis of said one end of the ram and the vertical planecontaining the pivotal connection of the ram to the arm, said arm beingfree to move downwardly on actuation of the ram to increase the anglebetween the ram and the cover to increase the force exerted by the ramin'the early stages of opening the cover.

3. The device 'n aceortjance with claim 1 having means to release fluidin the rairnlwhen the coverreaches a fully open position and havingmeans to retain the cover in position.

4. The device in accordance with claim 2 having means to release fluidin the ram when the cover reaches a fully open position and having meansto retain the cover in said open position.

5. The device in accordance with claim 1 having means to lock the coverin a closed position comprising a bar having substantially horizontalportions spaced below the cover, a fixed keeper plate having a recessaccepting one half of the bar and a pivoted keeper plate accepting theother half of the bar and means controlled by the temperature controlledmeans to hold the pivoted plate in position receiving the bar until saidpredetermined temperature is reached.

6. The device in accordance with claim 2 having means to lock the coverin a closed position comprising a bar having'a substantially horizontalportion spaced below the cover, a fixed keeper plate having a recessaccepting one half of the bar and a pivoted keeper plate accepting theother half of the bar and means controlled by the temperature controlledmeans to hold the pivoted plate in position receiving the bar until saidpredetermined temperature is reached.

7. The device in accordance with claim 3 having means to lock the coverin a closed position comprising a bar having a substantially horizontalportion spaced below the cover, a fixed keeper plate having a recessaccepting one half of the bar and a pivoted keeper plate accepting theother half of the bar and means controlled by the temperature controlledmeans to hold the pivoted plate in position receiving the bar until saidpredetermined temperature is reached.

8. The device in accordance with claim 4 having means to lock the coverin a closed position comprising a bar having a substantially horizontalportion spaced below the cover, a fixed keeper plate having a recessaccepting one half of the bar and a pivoted keeper plate accepting theother half of the bar and means controlled by the temperature controlledmeans to hold the pivoted plate in position receiving the bar until saidpredetermined temperature is reached.

9. The device in accordance with claim 1 in which the temperaturecontrolled means includes a spring biased actuating lever, a fusiblelink connected to the lever, connector means connected to the fusiblelink, a bracket, a pin passing through an opening in the bracket and anopening in the connector means and means to pull the pin out of saidopenings to permit the spring to move said actuating lever.

10. The device in accordance with claim 2 in which the temsaid openperature controlled means includes a spring biased actuating lever, afusible link connected to the lever, connector means connected to thefusible link, a bracket, a pin passing through an opening in the bracketand an opening in the connector means and means to pull the pin out ofsaid openings to permit the spring to move said actuating lever.

11. The device in accordance with claim 4 in which the temperaturecontrolled means includes a spring biased actuating lever, a fusiblelink connected to the lever, connector means connected to the fusiblelink, a bracket, a pin passing through an opening in the bracket and anopening in the connector means and means to pull the pin out of saidopenings to permit the spring to move said actuating lever.

12. The device in accordance with claim 6 in which the temperaturecontrolled means includes a spring biased actuating lever, a fusiblelink connected to the lever, connector means connected to the fusiblelink, a bracket, a pin passing through an opening in the bracket and anopening in the connector means and means to pull the pin out of saidopenings to permit the spring to move said actuating lever.

13. The device in accordance with claim 8 in which the temperaturecontrolled means includes a spring biased actuating lever, a fusiblelink connected to the lever, connector means connected to the fusiblelink, a bracket, a pin passing through an opening in the bracket and anopening in the connector means and means to pull the pin out of saidopenings to permit the spring to move said actuating lever. I

14. The device in accordance with claim 1 in which the connectionbetween the fluid storage means and the ram has a restrictor to throttlethe flow of fluid to the ram.

15. The device in accordance with claim 2 in which the connectionbetween the fluid storage means and the ram has a restrictor to throttlethe flow of fluid to the ram.

16. The device in accordance with claim 3 in which the connectionbetween the fluid storage means and the ram has a restrictor to throttlethe flow of fluid to the ram.

17. The device in accordance with claim 4 in which the connectionbetween the fluid storage means and the ram has a restrictor to throttlethe flow of fluid to the ram.

18. The device in accordance with claim 5 in which the connectionbetween the fluid storage means and the ram has a restrictor to throttlethe flow of fluid to the ram.

19. The device in accordance with claim 10 in which the connectionbetween the fluid storage means and the ram has a restrictor to throttlethe flow of fluid to the ram.

1. In a fire vent hatch comprising a housing having upstanding sidewallsand a cover pivotally secured to one of the sidewalls the improvementcomprising: a ram having one end pivotally connected to the cover on anaxis parallel to the pivotal axis of the cover and having the other endpivotally connected to a sidewall on an axis parallel to the pivotalaxis of the cover and lower than the pivotal axis of said one end,removable means to store a fluid under pressure connected to the ram,and temperature controlled means to control the flow of fluid from thestorage means to the ram to provide for the flow of fluid to the ram toraise the cover at a predetermined temperature.
 2. The device inaccordance with claim 1 in which said other end of the ram is pivotallyconnected to an arm on an axis parallel to the pivotal axis of thecover, the arm is pivotally connected to a side at a point in a verticalplane lying intermediate the vertical plane containing the pivotal axisof said one end of the ram and the vertical plane containing the pivotalconnection of the ram to the arm, said arm being free to move downwardlyon actuation of the ram to increase the angle between the ram and thecover to increase the force exerted by the ram in the early stages ofopening the cover.
 3. The device in accordance with claim 1 having meansto release fluid in the ram when the cover reaches a fully open positionand having means to retain the cover in said open position.
 4. Thedevice in accordance with claim 2 having means to release fluid in theram when the cover reaches a fully open position and having means toretain the cover in said open position.
 5. The device in accordance withclaim 1 having means to lock the cover in a closed position comprising abar having substantially horizontal portions spaced below the cover, afixed keeper plate having a recess accepting one half of the bar and apivoted keeper plate accepting the other half of the bar and meanscontrolled by the temperature controlled means to hold the pivoted platein position receiving the bar until said predetermined temperature isreached.
 6. The device in accordance with claim 2 having means to lockthe cover in a closed position comprising a bar having a substantiallyhorizontal portion spaced below the cover, a fixed keeper plate having arecess accepting one half of the bar and a pivoted keeper plateaccepting the other half of the bar and means controlled by thetemperature controlled means to hold the pivoted plate in positionreceiving the bar until said predetermined temperature is reached. 7.The device in accordance with claim 3 having means to lock the cover ina closed position comprising a bar having a substantially horizontalportion spaced below the cover, a fixed keeper plate having a recessaccepting one half of the bar and a pivoted keeper plate accepting theother half of the bar and means controlled by the temperature controlledmeans to hold the pivoted plate in position receiving the bar until saidpredetermined temperature is reached.
 8. The device in accordance withclaim 4 having means to lock the cover in a closed position comprising abar having a substantially horizontal portion spaced below the cover, afixed keeper plate having a recess accepting one half of the bar and apivoted keeper plate accepting the other half of the bar and meanscontrolled by the temperature controlled means to hold the pivoted platein position receiving the bar until said predetermined temperature isreached.
 9. The device in accordance with claim 1 in which thetemperature controlled means includes a spring biased actuating lever, afusible link connected to the lever, connector means connected to thefusible link, a bracket, a pin passing through an opening in the bracketand an opening in the connector means and means to pull the pin out ofsaid openings to permit the spring to move said actuating lever.
 10. Thedevice in accordance with claim 2 in which the temperature controlledmeans includes a spring biased actuating lever, a fusible link connectedto the lever, connector means connected to the fusible link, a bracket,a pin passing through an opening in the bracket and an opening in theconnector means and means to pull the pin out of said openings to permitthe spring to move said actuating lever.
 11. The device in accordancewith claim 4 in which the temperature controlled means includes a springbiased actuating lever, a fusible link connected to the lever, connectormeans connected to the fusible link, a bracket, a pin passing through anopening in the bracket and an opening in the connector means and meansto pull the pin out of said openings to permit the spring to move saidactuating lever.
 12. The device in accordance with claim 6 in which thetemperature controlled means includes a spring biased actuating lever, afusible link connected to the lever, connector means connected to thefusible link, a bracket, a pin passing through an opening in the bracketand an opening in the connector means and means to pull the pin out ofsaid openings to permit the spring to move said actuating lever.
 13. Thedevice in accordance with claim 8 in which the temperature controlledmeans includes a spring biased actuating lever, a fusible link connectedto the lever, connector means connected to the fusible link, a bracket,a pin passing through an opening in the bracket and an opening in theconnector means and means to pull the pin out of said openings to permitthe spring to move said actuating lever.
 14. The device in accordancewith claim 1 in which the connection between the fluid storage means andthe ram has a restrictor to throttle the flow of fluid to the ram. 15.The device in accordance with claim 2 in which the connection betweenthe fluid storage means and the ram has a restrictor to throttle theflow of fluid to the ram.
 16. The device in accordance with claim 3 inwhich the connection between the fluid storage means and the ram has arestrictor to throttle the flow of fluid to the ram.
 17. The device inaccordance with claim 4 in which the connection between the fluidstorage means and the ram has a restrictor to throttle the flow of fluidto the ram.
 18. The device in accordance with claim 5 in which theconnection between the fluid storage means and the ram has a restrictorto throttle the flow of fluid to the ram.
 19. The device in accordancewith claim 10 in which the connection between the fluid storage meansand the ram has a restrictor to throttle the flow of fluid to the ram.